Dan Rathbun squeezed in time to chat with a reporter the other night, despite the fact that he was feverishly working on the bus in which his band, Sleepytime Gorilla Museum, rides on concert tours. And he needed a bath.

A retrofitted 1960s Greyhound-style bus that conveyed Sleepytime on three tours last year alone, the vehicle in question had just undergone some last-minute repairs to get it up to speed for the group's latest tour. That journey kicks off this week with a gig in San Diego and comes to Tucson Monday, Feb. 21, for a performance at Solar Culture Gallery, a venue that Sleepytime Gorilla Museum has played on several occasions.

"Now what it needs is a bicycle rack and a new heater," Rathbun said over the phone, amid some mysterious clanking in the background. Half the time, he sounded like a pragmatic mechanic; the other half, an eccentric inventor.

Rathbun, who plays bass guitar, among other instruments, is one of the founding members of Sleepytime Gorilla Museum, the endlessly inventive Bay Area music collective that explodes all musical categories, including those it seemingly embraces during heavily theatrical performances: art-rock, thrash-metal, free jazz, punk-bred noise, '50s rock 'n' roll, nightmarish nursery rhymes, avant-garde opera, folk music from Eastern Europe and Scandinavia and whatever else pushes its way up from the band's collective subconscious.

Sleepytime is touring to promote its third CD, Sleepytime Gorilla Museum of Natural History, which was released last October on Web of Mimicry, the same label that gives the world such envelope-pushing art bands such as Secret Chiefs 3 and Estradasphere.

Heavily annotated with the band's trademark blend of faux-vintage illustration, old-timey typesetting and quasi-scientific-metaphysical manifestos, Of Natural History is a dynamic concoction that only partly approximates the brilliant insanity of the band's live performances, which have incorporated elements from theater of the absurd, Butoh dance, puppetry and Grand Guignol spectacle.

Without needing to defend his band's theatricality, Rathbun argues that rock 'n' roll, as an art, is a theater event, even as disingenuous garage-rock bands want to remove its trappings to make it more "real."

"It is theatrical. We're somewhat costumed on stage, and the lighting and sound technicians are as much a part of what we do as the musicians. ... Rock 'n' roll has always had a big component of show business.

"And it's a rare person who actually succeeds in not caring about how they present themselves."

The 6-year-old group's other founding members, by the way, are violinist Carla Kihlstedt, who also leads her own band 2 Foot Yard and is a member of the acclaimed avant-garde chamber group Tin Hat Trio; and guitarist Nils Frykdahl, whose outside experience includes Faun Fables and Ink Boat.

Recently added to the fold are multi-instrumentalist Michael Mellender (co-founder of Immersion Composition Society) and drummer Matthias Bossi (formerly of Skeleton Key). Rathbun praised the new members for their creative input on Of Natural History.

"We were really determined (when looking for new members) not to have a couple of new guys who were just going to do what we told them to do. Matthias and Michael bring a lot of new energy to the group."

Before Sleepytime, Rathbun and Frykdahl worked together in the San Francisco-based band Idiot Flesh. "Sleepytime is really the stylistic evolution of Idiot Flesh. That band never really made it to the wild world outside the way this one has," Rathbun said.

The goal of Sleepytime, he said, is to create a complete experience of sight and sound.

From a presentation point of view, Rathbun has been hugely impressed and influenced by fellow San Francisco-area act The Residents. "They have a way of putting on shows that impresses me in that from the start of a show to the end of a show, there is never a break in character."

According to the band's (perhaps apocryphal) history, its name was borrowed from Sleepytime Gorilla Press, which was the vehicle for the ravings of futurist philosopher and mathematician John Kane in the early 20th century. The band's name also is an "awkward little poem," Frykdahl has said.

The members of Sleepytime are sort of retro-futurists, always seeking to create music that sounds wholly new, because they've heard it all--and so, too, have their fans, Rathbun said.

The members of Sleepytime range in age from 25 to 40.

"Our fans come from a pretty broad base, but they do tend to be a little older, like us. One of the band's biggest appeals to people, I think, is that it's something new for people who had tired of a lot of popular music."

Like a single-malt scotch or escargot, the music of Sleepytime Gorilla Museum is a taste for a refined palette.

"When, all of us, we started playing music, we were in that young, idealistic phase where everything is new and exciting in music, and it was all a thrill. We didn't get tired of music until we had developed our abilities a little bit."

"Sometimes I feel like I have rejected most music. You know, like I'm tired of it all."

Composing new works to hang in the Sleepytime Gorilla Museum is the only way Rathbun can stay interested in music.

In fact, although the band will play most of the Of Natural History CD when it hits Tucson, it also has readied four new songs ready that have Rathbun feeling especially jazzed. "We're really looking forward to performing them," he said.